Cryotherapy is a therapy method in which a human body is treated 1-4 minutes with cold (such as −110° C.). The treatment has been proven to soothe pain for few hours and the treatment may reduce inflammation, for example, in rheumatism. A recurring cold treatment is assumed to increase a human body's ability to reduce toxic radicals of oxygen and thus also improve the health and capability. The cold treatment is gradually increased so that a person to be treated to is finally guided to a chamber providing a cryogenic temperature. A swimsuit, a mask covering a mouth and nose, a beanie or some other headwear, cloves, and footwear are used as clothing.
Various technologies are usable for creating cryogenic air. A liquid nitrogen technology is based on use of nitrogen and an evaporator. In more detail, a treatment chamber comprises an evaporator in which the liquid nitrogen evaporates and simultaneously takes heat from its environment and cools the treatment chamber. The price of a liquid nitrogen cooling apparatus is relative low but the transportation of the liquid nitrogen requires special arrangements and thus the usage costs of the apparatus are relative high. Another problem related to use of nitrogen is that the door of the treatment chamber may freeze to the door frame and the evaporator may also freeze. Removing of the ice causes maintenance outages.
Forming of the ice can be effectively avoided by using a compressor and a closed coolant circulation in cooling. When the cooling apparatus comprises two or more coolant circulations, the technique is termed a cascade-compressor technique. By using this technique −120° C. or even colder temperature is achieved so that air is circulated air in the treatment chamber. As an end result, the air is extremely dry and thus unpleasant to inhale and a person to be treated is forced to use a mask covering the person's mouth and nose in order to ease inhalation.
DE19515287C2 is mentioned as an example of a publication that describes the cascade-compressor technique. The following publications are mentioned as examples of the prior art: U.S. Pat. No. 8,316,652B2 “System and method for whole-body cryotherapy”, U.S. Pat. No. 8,162,930B2 “Method and the device for cryogenic therapy applied on the whole body of a patient”, CN100501273C “Controllable temperature deep cooling processing system based on self supercharging cryogenic fluids conveying technology”, KR1011222B1 “Cooling machine using cold air”, KR453113Y1 “Cryogenic of freezing device”, and CN203065526U “Large-scale workpiece cryogenic treatment equipment”.
In publication US2015265460A1 a valve for equalizing pressure is placed at a wall of a treatment chamber in the proximity of the ceiling. When the valve is located in this manner, air flowing through it hits in the treatment chamber to the evaporator and the moisture included in the air freezes on the surface of the evaporator.
The inventor of the present invention has expressed in magazine articles an idea of such hybrid system that utilizes a cooling implemented with a compressor technique as well as a cooling implemented with the liquid nitrogen technique.
A moisture control in a cryotherapy system is mentioned as one technical challenge in the invention. In more detail, there is a need to affect the composition of the air and in the same time forming of solid ice is aimed to be avoided.